When I have to do 100% water changes, I use a clear plastic cup. Like the kind you drink punch out of at parties and proms. Just dip it in and 9 times out of 10, the suction sucks the little guy right in. Then you can just leave him in the cup while doing the water change. If he's a jumper, cover it with something so he can't escape.
Green tea actually makes the water all brown. The brown is the released tannins. :) The darker water simulates a betta's natural habitat and helps to destress them. You get the same brown water when you use IAL or oak leaves.
I'm liking what I see with the new fin growth.
You're doing a fantastic job with him, roarsirroar.